Impedance Scan of Inverter-Based Resources and Diesel Generator for Stability Analysis

Research output: Contribution to conferencePaper

Abstract

Impedance-based methods are widely used for power system stability analysis with inverter-based resources (IBRs), e.g., assessing dynamic interactions between the power grid and an IBR, control interactions between multiple IBRs, and the sub-synchronous oscillation and damping phenomenon. Since it is difficult to get a numerical model 100% matching with the hardware IBR, using the hardware inverter directly to obtain its output impedance has become a prominent approach nowadays. Therefore, this article presents the impedance scan using hardware IBRs, and also a hardware diesel generator as it still stays with the grid before the grid completely goes to renewable. The devices under test (DuTs) for the impedance scan includes two 3-..phi.., 480 V, 60 Hz commercial grid-forming IBRs (one of 250 kVA and another of 125 kVA rating) in series with ..delta..-Y transformers, one 3-..phi.., 480 V, 60 Hz commercial grid-following IBR (of 125 kVA rating), and a 3-..phi.., 480 V, 60 Hz commercial diesel generator (of 187.5 kVA rating). Using voltage signals perturbed with sub-, inter-, and higher harmonic components, and measuring the current response, the positive-sequence impedances are computed via an offline-based post-analysis. Moreover, best-fit transfer functions are estimated that closely resemble the measured data points of the positive-sequence impedances. Based on the observations from various outcomes of the hardware experiments, this article also provides some fundamental insights on the equivalent positive-sequence impedance of a combination of multiple hardware components by comparing the estimated and the empirically computed impedances. A comparative insight on the damping capability of the DuTs using the positive-sequence impedances of the hardware is also discussed.
Original languageAmerican English
Number of pages5
DOIs
StatePublished - 2024
Event2024 IEEE Power & Energy Society General Meeting - Seattle, Washington
Duration: 21 Jul 202425 Jul 2024

Conference

Conference2024 IEEE Power & Energy Society General Meeting
CitySeattle, Washington
Period21/07/2425/07/24

Bibliographical note

See NREL/CP-5D00-88130 for preprint

NREL Publication Number

  • NREL/CP-5D00-91988

Keywords

  • current measurement
  • damping
  • generators
  • hardware
  • impedance
  • impedance measurement
  • inverter-based resource
  • stability analysis
  • transfer functions
  • voltage measurement

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